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We provide CoRoT and Spitzer light curves, as well as broad-bandmulti-wavelength photometry and high resolution, multi- and single-epochspectroscopy for 17 classical T Tauris in NGC 2264 whose CoRoT light curves(LCs) exemplify the "stochastic" LC class as defined in Cody et al. (2014). Themost probable physical mechanism to explain the optical variability in this LCclass is time-dependent mass accretion onto the stellar photosphere, producingtransient hot spots. As evidence in favor of this hypothesis, multi-epoch highresolution spectra for a subset of these stars shows that their veiling levelsalso vary in time and that this veiling variability is consistent in bothamplitude and timescale with the optical LC morphology. Furthermore, theveiling variability is well-correlated with the strength of the HeI 6678Aemission line, a feature predicted by models to arise in accretion shocks on ornear the stellar photosphere. Stars with accretion burst LC morphology(Stauffer et al. 2014) are also attributed to variable mass accretion. Both thestochastic and accretion burst LCs can be explained by a simple model ofrandomly occurring flux bursts, with the stochastic LC class having a higherfrequency of lower amplitude events. Based on their UV excesses, veiling, andmean Ha equivalent widths, members of the stochastic LC class have onlymoderate time-averaged mass accretion rates. The most common feature of theirHa profiles is for them to exhibit blue-shifted absorption features, mostlikely originating in a disk wind. The lack of periodic signatures in the LCssuggests that little of the variability is due to long-lived hot spots rotatinginto or out of our line of sight; instead, the primary driver of the observedphotometric variability is likely to be instabilities in the inner disk thatlead to variable mass accretion.

CSI 2264: Characterizing Young Stars in NGC 2264 with Stochastically Varying Light Curves